1. Field of the Invention
The present invention relates to a refrigeration system for use in, such as, an electric refrigerator.
2. Description of the Prior Art
At the meeting for revising the Montreal Protocol about the ozone layer destructing material in the Ozone Layer Protection Treaty, it was agreed upon to wholly abolish chlorofluorocarbon (CFC) in 1996. It was also agreed upon to realize a large CFC reduction from 1994 to no more than 25% as compared with 1986. In response to this, researches have been actively performed by the associated makers, such as, the refrigerant makers, the refrigeration system makers and the oil makers. As a result of the researches, a refrigerant including, as a main component, chlorine-free fluorocarbon, particularly, known as HFC-134a, has been widely admitted as an alternative refrigerant for a CFC refrigerant including chlorine-containing fluorocarbon, particularly, CFC-12 which has been widely used. Further, in view of required solubility with the HFC-134a refrigerant, a lubricating oil containing an ester oil as a base oil has been developed.
FIG. 8 is a diagram schematically showing a typical conventional refrigeration system 15 as disclosed in, such as, Japanese First (unexamined) Patent Publication No. 4-183788. In FIG. 8, the refrigeration system 15 includes a compressor 10, a condenser 11, a drier 14, an expansion mechanism 12 in the form of a capillary tube and an evaporator 13, which are hermetically connected by piping as shown. Further, in the refrigeration system 15, the foregoing HFC-134a refrigerant and the foregoing ester lubricating oil are hermetically enclosed for circulation in a direction of an arrow as indicated in FIG. 8.
In FIG. 8, numeral 16 denotes a typical conventional gas charge port tube, which will be described later with reference to FIG. 9 and as compared with a preferred embodiment of the present invention.
As is known in the art, it is very difficult to find a lubricating oil which satisfies required solubility with HFC-134a and other properties required for a lubricating oil for use in the refrigeration system. On a practical basis, a lubricating oil satisfying such requirements is limited to the ester lubricating oil. Further, HFC-134a costs 5 to 6 times as high as CFC-12. Moreover, although HFC-134a improves an ozone destruction parameter (ODP), it is said to have some problem in improving a global warming parameter (GWP).
In addition, since the ester oil is inferior in hydrolysis stability and hygroscopic property as compared with a mineral oil or an alkylbenzene oil which has been widely used with, such as, CFC-12, some special equipment is required for dehydration when the ester oil is used. Further, the ester oil costs 3 to 4 times as high as the mineral oil or the alkylbenzene oil. Moreover, the ester oil tends to dissolve organic substances inside the refrigeration system so as to produce contaminants which are likely to block the capillary tube to lower the cooling effect of the refrigeration system. Accordingly, in order to prevent this, component parts of the refrigeration system should be washed in a particular manner, which thus requires additional processes and costs.